The causes (natural and anthropogenic) of declining biodiversity

Question 1

Biodiversity

Answer 1

The variety of all living things; the different plants, animals and micro-organisms, the genetic information they contain and the ecosystems they form.

Question 2

Earth’s five major extinction events

Answer 2

The Cretaceous-Tertiary, Tirassic-Jurassic, Permian-Triassic, Late Devonian and Ordovician-Silurian extinction events; respectively.

Question 3

Five main natural causes of mass extinctions (and thus biodiversity loss)

Answer 3

Flood basalt events
Major sea level falls
Asteroid impacts
Sustained global cooling
Sustained global warming

Question 4

2 Natural causes of mass extinctions in detail

Answer 4

Flood basalt events
-The result of a giant volcanic eruption or series of eruptions
-There have been 11 documented occurences
They are associated with
-Production of dust and particulate aerosols which inhibited photosynthesis causing both terrestrial and aquatic food chains to collapse
-Emission of sulphur oxides which were then precipitated as acid rain, poisoning many organisms and further contributing to the collapse of food chains
-Emission of large quantities of carbon dioxide which may cause sustained global warming

Major sea level falls
-Sea level falls could reduce the continental shelf area sufficiently to cause a marine mass extinction, and could disrupt weather patterns enough to cause extinctions on land
-Most likely the result of other events, such as sustained global cooling or the sinking of the mid-ocean ridges
-There have been 12 documented major sea level falls with 7 associated with significant extinctions

Question 5

Recent natural causes of loss of biodiversity

Answer 5

Variations in earth orbit and tilt
Variations in solar output and sunspot activity
The impact of volcanic activity

Question 6

One recent natural cause of loss of biodiversity in detail

Answer 6

Variations in the earth’s orbit and tilt have altered earth’s climatic conditions and resulted in habitat and species migration.

Question 7

Drivers (human causes) of biodiversity loss (direct and indirect)

Answer 7

Direct drivers:
Land cover change and habitat change
Invasive species
Overexploitation
Nutrient pollution
Climate change

Indirect drivers:
Change in economic activity
Population change
Science and technology
Cultural and religious factors
Socio-political factors

Question 8

Two direct drivers (human causes) of biodiversity loss in detail

Answer 8

Land cover change and habitat change
-As world and local populations have increased the pressure on biomes for fuel supplies and food production has continued to increase
-Degradation of habitats leads to loss of biodiversity
-Cultivated systems (croplands, live stock production, etc) has led to major shifts in ecological boundaries and habitat fragmentation
-Habitat fragmentation places larger foraging species at threat as their food supply dwindles and they’re exposed to outside threats

Climate change
-Has caused changes in species distributions, population sizes, the timing of reproduction or migration events and an increase in the frequency of pest and disease outbreaks
-Coral reefs have gone undergone major bleaching episodes when sea surface temperatures have increased

Question 9

One indirect driver (human cause) of biodiversity loss in detail

Answer 9

Population change: The fact that more people live in cities increases the demand for food and energy and thereby pressures on ecosystems resulting in increased land cover change and loss of biodiversity

Question 10

A new driver (human cause) of biodiversity loss

Answer 10

Genetic manipulation
-Humans are now directly manipulating genomes by artificial selection and molecular techniques, and indirectly by managing ecosystems and populations to conserve them
-As human management of ecosystems and populations increases, natural ecological processes are altered
-The production and cultivation of genetically modified canola is a recent example